A needleless injector is an injector having no needle but provided to give an injection with high pressure.
Conventional needleless injectors include those shown in U.S. Pat. No. 5,704,911 “NEEDLESS HYPODERMIC JET INJECTOR”(registration date: Jan. 6, 1998), U.S. Pat. No. 5,891,086 “NEEDLE-LESS INJECTOR”(registration date: Apr. 6, 1999), U.S. Pat. No. 7,090,662 “DOSE DIAL AND DRIVE MECHANISMS SUITABLE FOR USE IN DRUG DELIVERY DEVICES”(registration date: Aug. 15, 2006) and etc.
However, such conventional needleless injectors have a complicated structure and thus are not easy to manufacture, generate noise during injection due to an impact. Also, they are comparably expensive.